The present invention relates to an apparatus and method for cleaning internal combustion engine crankcase breather (blow-by) gas and an internal combustion engine including said apparatus.
During the compression and power strokes in an internal combustion engine, the difference in gas pressures above and below a piston is sufficient to cause leakage (blow-by) of gas past the piston into the engine crankcase. The resulting increase in pressure within the crankcase can force oil past by the engine oil seals and this pressure may also damage the seals and hence lead to further leakage of oil.
To diminish the damaging effects of blow-by it is normal to relieve the crankcase pressure either by venting the breather gas to atmosphere via an open breather or by connecting the crankcase to the engine air intake system whereby breather gas is conveyed to the engine combustion chamber via the engine air inlet system and under the control of a pressure regulating means. This latter system constitutes a closed-circuit breather system.
It is desirable to include, in breather systems, means to retrieve oil contained in breather gas and return this to the engine lubricating oil system for re-use. Otherwise the carry-over of oil will lead to pollution and, in a closed-circuit system, to fouling of turbocharger compressor vanes, engine poppet valves and other components in contact with inlet air.
As well as leading to contamination and emission problems, the carry-over of oil in breather gas will reduce the volume of oil available for the lubricating and cooling requirements of the engine. It is desirable to minimised oil carry-over, and an oil/air separator is therefore included in most closed-circuit breather systems.
A further problem with oil carry-over in the closed-circuit breather system of an engine, especially of the diesel type, is that the oil can fuel the engine and lead to an unintentional and possibly severe increase in engine speed known as `run-away`.
The run-away problem may be exacerbated where, the engine is operated at high gradients (angles of inclination), especially where conditions of abuse prevail, and in particular where the designed maximum oil level in the sump has been exceeded, where the intake air filter is dirty and/or where blow-by levels are high due to engine wear. Under these abuse conditions, even where a conventional separator is provided the breather system may take up more oil than the separator can handle and oil can be drawn into the engine air intake system and hence to the combustion chamber where it can fuel the engine and lead to run-away.